Two new antioxidant diarylheptanoids from the fruits of Alpinia oxyphylla

Two new diarylheptanoids, 1-(3′,5′-dihydroxy-4′-methoxyphenyl)-7-phenyl-3-heptanone (1) and 1-(2′,4′-dihydroxy-3′-methoxyphenyl)-7-(4″-methoxyphenyl)-3-heptanone (2), along with known diarylheptanoid yakuchinone A (3), and five flavanoids, tectochrysin (4), chrysin (5), izalpinin (6), kaempferol 7, 4′-dimethyl ether (7), and kaempferide (8) were isolated from the fruits of Alpinia oxyphylla Miq. Their structures were determined by means of spectroscopic methods. Antioxidant activities of all the isolated compounds were evaluated using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Compounds 1–3 and 6–8 exhibited potent antioxidant activities in the DPPH assay.